1. Field of the Invention.
This invention relates to semiconductor memories. In particular, the present invention relates to an improved read only memory (ROM) which utilizes integrated Schottky logic (ISL) gates as wordline drivers and decoders.
2. Description of the Prior Art.
The development of semiconductor memory technology has included continual efforts to develop read only memory (ROM) devices with higher packing density, lower power dissipation, higher speed operation, and higher processing yields. The use of diode data fields to define the pattern of data within a ROM is particularly advantageous because diodes usually exhibit high processing yields and permit relatively high packing density. This is particularly true of Schottky diode arrays.
In a commonly assigned copending application Ser. No. 513,872, filed July 14, 1983, entitled "Semiconductor Memory" by P. Roberts and T. Vu (which is incorporated by reference herein), a read only memory is described which uses Schottky diode memory arrays together with integrated Schottky logic (ISL) or metal semiconductor field effect transistor (MESFET) gates as wordline drivers and decoders. This memory offers high packing density, very low power dissipation and very high speed.
ISL is a very large scale integration (VLSI) bipolar logic family which uses an NPN transistor, with a PNP clamp, to perform logic inversion. The AND function is accomplished by wiring together either merged (integrated) or discrete Schottky diodes. The result is a powerful VLSI technology that is compatible with standard bipolar processes.
In the ISL ROM proposed by Vu and Roberts, data is programmed by the presence or absence of a Schottky diode at each particular intersection of a wordline and a bitline. The presence of a Schottky diode results in a logic zero output. The absence of a diode results in a logic one output. The peripheral circuitry is ISL logic which performs as row and column decoders and as sense amplifiers for reading the data from the bitlines.